TRA proposes the development of a novel platelet harvesting system based on a previously developed ultrasound blood cell/plasma separation technology. This technology, developed under an NIH (NHLBI) grant, will produce an ultrasonic filter. The device uses standard filter membranes placed in an acoustic field that traps and transports the platelets away from the filter surface. Platelet containing plasma will continuously flow past the filter while the plasma is removed from the feed. Platelet rich plasma will exit the device. By careful balancing of the acoustic force and the Stoke's viscous drag force, platelet aggregation will be minimized.